PTR-01 Promotes Wound Healing, Eases Pain in Phase 2 RDEB Trial
Treatment with the experimental protein replacement therapy PTR-01 promoted wound healing and decreased pain in people with recessive dystrophic epidermolysis bullosa (RDEB), new results from a Phase 2 clinical trial show.
The findings were presented by BridgeBio Pharma and its affiliate, Phoenix Tissue Repair, the therapy’s developer, at the annual meeting of the Society for Investigative Dermatology, in Portland, Oregon in May.
“In patients with recessive dystrophic epidermolysis bullosa (RDEB) even minor friction or trauma can cause debilitating blistering, tearing and scarring of the skin, along with severe pain and itching. Our data shows that treatment with PTR-01 led to rapid, consistent, and durable wound healing,” Sanuj Ravindran, MD, Phoenix’s executive chairman, said in a press release.
RDEB is caused by mutations in the gene that codes for collagen VII, an important structural protein. PTR-01 contains a recombinant (lab-made) version of this protein, designed to be administered via infusion into the bloodstream.
“We are hopeful that by addressing the root cause of this rare disease, we will be able to provide a treatment beyond daily wound care and pain management for patients in need,” Ravindran said.
The Phase 2 trial, called PTR-01-002 (NCT04599881), enrolled six people with RDEB at Stanford University and Children’s Hospital Colorado. All were treated with PTR-01 at a dose of 3 mg/kg per infusion. Participants received weekly infusions for four weeks, then infusions every other week for an additional 14 weeks.
Five of the participants completed the study. According to BridgeBio, PTR-01 treatment was generally well tolerated and rapidly increased levels of collagen VII in the dermal-epidermal junction (DEJ), which helps support skin structure. The company did not specify whether any side effects were reported or any reasons for discontinuing the trial.
All five participants who completed the study reported a marked decrease in pain after PTR-01 treatment. Mean total pain scores measured by the Instrument for Scoring Clinical Outcomes of Research for Epidermolysis Bullosa (iscorEB) decreased by 36%. Measures of mood, disease impact, and ability to function in day-to-day life also improved with treatment.
Across the six trial participants, 26 wounds were defined as “target wounds.” By the end of treatment (after about four months), more than 80% of these wounds — 21 out of 26 — had shrunk in size by at least 50%. This level of wound reduction was seen for recurrent (86%) and chronic (75%) wounds, and also for large (89%) and small (77%) wounds.
Throughout the study, clinicians assessed each of the target wounds on a seven-point scale of severity. By day 15 after starting treatment, 15 (58%) of the wounds had improved by at least two points. By the trial’s end, 18 (69%) showed such an improvement.
In this trial, treatment “responders” were defined as those with two-point or more improvement in clinician-rated wound severity for at least half of that person’s wounds. Based on this criteria, four of the six participants (67%) were deemed responders.
Phoenix Tissue Repair has announced that it has launched a Phase 2 extension study where participants can continue being treated with PTR-01 and monitored for outcomes.